Fibrous dysplasia generally leads to skeletal deformity over time, particularly when the lower extremities are affected. The authors describe their experience in this field, proposing mainly preventive treatment of progressive deformities and pathological fractures. They prefer intramedullary nailing, which by strengthening the affected bone allows free and early mobilization of the limb. Moreover, full weight-bearing prevents the onset of "ex non usu" osteoporosis, which is quite often responsible for pathological fractures.